That should fit. I just put 15x7 with 4" back spacing with P255/60/15 on my 68 dart with the small bolt pattern. Only had to trim about 3/8" from the lip. You're fine I think.
Hello CWATTS, I am new to this forum. I just bought a 68 Dart and was wondering what size your rally wheels are. Thanks for the exact info on which tires they are, now we need to know are the rims 14x6, 14x5.5, etc.?